Advanced illuminated reticle

ABSTRACT

A reticle design is disclosed for use in the first focal plane, which can be used both for close range and long range shooting. A phosphor luminescent material or other type of visible reflecting material is used with a diffraction pattern to enhance the brightness or visibility of all or a portion of the reticle, and may be used alone or in connection with other ways of illuminating the reticle.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/681,020, filed Aug. 8, 2012, the disclosure of which is hereby incorporated by reference herein in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to the field of reticles for riflescopes. More particularly, the present invention relates to advanced illumination for a reticle for a riflescope.

BACKGROUND

Riflescopes and reticles are changing continuously as shooting changes and technology develops. There have been a number of advances in reticle design over the past ten years, but none of these advances has fully resolved all of the problems or limitations in certain types of shooting. What is very desirable right now, especially in military, law enforcement, and competition shooting, is the ability to use one scope for very close range shooting and also be able to use that same scope for longer range shooting. Close shooting and long range shooting can be defined very differently depending on the person, training, methods, and tactics. It will be assumed that close range shooting refers to shooting at a range of 100 meters or less and long range shooting refers to distances beyond 100 meters, although the scope of the present invention is not limited to these ranges.

A “center pattern” will be referred to herein to describe any pattern that can be used advantageously for close range shooting. A center pattern may be simply a center dot, broken circle, horseshoe, or any pattern that is considered easy to use as an aiming point for close range shooting. This center pattern needs to be very bright so that it can be seen in bright daylight situations and against the brightest of backgrounds. For this reason, scopes that have been very popular for close range shooting include scopes with a very bright center dot or “center pattern” for an aiming point. For example, Aimpoint uses reflex style optics, and Eotech uses holographic reticles with a laser, a beam splitter and a reticle mask. Reflex style scopes only provide a 1× magnification view, that is, they provide no magnification at all but simply an illuminated center pattern to aim at the target. In order to use a center pattern to shoot at longer range targets, a shooter needs to aim the illuminated center pattern above the target, but is left to guess how much above. Reflex style scopes do offer options to mount a magnifying optic behind the sight for longer range shots. However, the use of a magnifying optic only magnifies the image and the center pattern but does not provide “drop compensation” markers such as milliradians markers or MOA markers so as to clearly show the amount of “hold over” for any particular long range shot. Further, using a magnifying optic, which has the effect of increasing the size of the center pattern, effectively covering up more of the sight picture, thus making it more difficult to achieve a finely placed aiming point, and thereby reducing the accuracy of longer range shots.

Trijicon has created a scope, called the ACOG, that uses a fixed magnified optic such as 4× or 6×. The ACOG uses fiber optics to illuminate a center pattern for aiming. These scopes can be advantageous for longer range shooting but have difficulty at closer ranges. Some Trijicon scopes use a simple “iron sight” on top of the scope for a simple close quarters aiming point. This is not ideal as it is not illuminated or as discriminating as an illuminated center pattern as in reflex style scopes.

Because of the drawbacks in the ACOG, Eotech, and Aimpoint designs, other scope companies have created optics based on a more traditional A-focal riflescope design that uses a 1× magnification but zooms to a higher magnification. Examples are 1-4×, 1-6×, or sometimes even higher magnifications. The desirable feature in these scopes is to have a true 1× magnification with little distortion so that they seem like an Aimpoint or Eotech scope at 1× magnification, but when zoomed to higher magnifications, they can be used for longer range like the ACOG or other traditional riflescopes. A traditional style riflescope that can be a true 1× power and zoom to higher magnifications has many advantages over the ACOG, Eotech, or Aimpoint style scopes, except for the problem of reticle illumination.

Before drawbacks to traditional riflescope designs are discussed further, one must understand the difference between first and second focal plane in traditional riflescopes. There are two planes of focus in a traditional riflescope. The first focal plane is in front (far side from the observer's eye) of the zoom system. The second focal plane is on the back side (nearest the observer's eye) of the zoom system. Second focal plane reticles are easier to manufacture and, therefore, are much more prevalent.

The problem with the second focal plane type of reticle is that the reticle maintains the same size no matter the magnification setting. This means any reticle features such as milliradians or MOA markings are only accurate at one magnification setting, which is determined by the optical designer. By contrast, first focal plane reticles are in front of the zoom system of lenses which means that as the image magnification is changed the reticle size changes accordingly. Thus, a first focal plane reticle has features such as milliradian or MOA markers which are accurate at all magnification settings. Because of this effect, first focal plane reticles are more desirable than second focal plane reticles.

Reticle illumination has been used for many years in traditional style riflescopes, but there have been illumination problems. A discussion of glass reticle technology will be useful background. Years ago, glass reticles were invented because they had the advantage of enabling “floating” reticle features. The term “floating,” when applied to a reticle, means that any design can be placed onto the glass surface without any other physical support, that is, the designs do not need to be connected. Floating reticles are unlike wire reticles, as the latter require all the reticle features to be supported by being connected to a frame in some way, much like a stencil or a neon sign. A glass reticle makes any pattern imaginable a reality. Generally, glass reticle makers will etch glass with a pattern, and then fill the etched areas with a various different materials, depending on different factors. Commonly, chrome is used as a material for filling the etched portion for use in non-illuminated features. For illuminated features, glass reticle makers commonly use a reflective material such as but not limited to titanium dioxide and sodium silicate. Usually in a glass reticle there is a second piece of glass cemented over the reticle pattern to protect the pattern, thereby creating a doublet.

Most other illuminated reticles are not bright enough to be used in bright daylight situations because current technology cannot make them bright enough. There are exceptions to this generality, but they also have their drawbacks. Traditional reticle illumination involves the use of an LED placed at the edge of the glass reticle. The light from the LED reflects off the reflective material towards the observer's eye, and thus creates an illuminated pattern. This method results in a desirable illuminated pattern for low light situations. But titanium dioxide and sodium silicate are actually very finely ground powders of these materials. When the light from the LED hits these materials, the light scatters light in all directions. Some of that light goes to the users eye. But it is obviously inefficient since it scatters light in all directions. The result is that not enough light is reflected for bright daylight situations.

One exception is the use of a light piped through an optic fiber to the center of the reticle to make a bright center dot. The problem with this design is that it can only be used in the second focal plane. The reason is that the first focal plane would require the reticle to be much smaller to appear the correct size to the user and it is difficult to get optic fibers that small, or at least to make the center dot that small. Also, using an optic fiber is difficult to do using glass reticle technology without making the fiber optic cable visible to the observer, which obstructs the view and is distracting. Moreover, fiber optics have the drawback of only having an illuminated center dot, or chevron, or other similarly small and compact shape. But disconnected entities are very difficult without multiple fibers. Other illumination types can result in a fully illuminated reticle pattern or a center pattern other than a simple dot.

Another system used for bright illuminated patterns is diffraction grated reticles. Swarovski uses a diffraction grated reticle in its Z6 line of scopes. This technology does produce a very bright center dot. The problem is the manner in which the light is provided to the diffraction pattern. U.S. Pat. No. 7,804,643 B2 discloses a prism system which reflects light to the diffraction pattern to create a bright center dot. The problem with this design is that it relies on a relatively large prism system which needs to be housed on the edge of the scope housing. This housing makes it difficult if not impossible to put a reticle in the first focal plane because the housing would interfere with the scope turrets. Another problem with this design is that the reticle moves much more in the first focal plane while adjusting the turrets. Since the prism needs to focus the light onto the diffraction pattern, this design requires focusing on a “moving target,” meaning that the reflected light may not always be aimed properly onto the diffraction reticle pattern. Even if this prism arrangement could be made to work in the first focal plane, there would still be the problem of having an undesirably large housing on the scope body.

Accordingly, there is a need for an improved design for illuminating a reticle for a riflescope, where the reticle is in the first focal plane.

SUMMARY OF THE INVENTION

The invention provides a telescopic sighting device for use by a user. The sighting device includes a sighting element having a focal plane. A reticle and a diffraction grating are formed in the focal plane. A first light source illuminates and excites a light emitting substance, which is aligned with the user and the diffraction grating in the focal plane, so as to direct the light from the light emitting substance through the diffraction grating to the user. The light emitting substance may be a phosphorescent light source that emits visible light. The phosphorescent light source may be of the type that is excited by either IR or UV light. A second light source may also be positioned in the area of the focal plane. Some of the light from the second light source may illuminate at least a portion of the reticle pattern but not the entire reticle pattern.

It will be understood that one or more aspects of this invention can meet certain objectives, while one or more other aspects can lead to certain other objectives. Other objects, features, benefits and advantages of the present invention will be apparent in this summary and descriptions of the disclosed embodiment, and will be readily apparent to those skilled in the art. Such objects, features, benefits and advantages will be apparent from the above as taken in conjunction with the accompanying figures and all reasonable inferences to be drawn therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded side view of certain components of a reticle assembly in accordance with the present invention, showing three lens components and referencing the placement of the reticle pattern and phosphor in one embodiment of a reticle design in accordance with the present invention.

FIG. 2 is an exploded perspective view of the reticle assembly components shown in FIG. 1.

FIG. 3 is an enlarged side view of a reticle assembly in accordance with the present invention, showing three lens elements cemented together.

FIG. 4 is a front elevation view of a reticle constructed according to another embodiment of a reticle assembly in accordance with the present invention, in which the phosphor pattern and diffraction pattern are aligned and in the shape of a broken circle.

FIG. 5 is a front elevation view of a reticle constructed according to yet another embodiment of a reticle assembly in accordance with the present invention, in which, besides the phosphor pattern and diffraction pattern being aligned and in the shape of a broken circle, the reticle includes phosphor dots with no corresponding diffraction grating.

FIG. 6 is a side view of a diffraction grating used in the present invention and light waves interacting with the diffraction grating.

FIG. 7 is an enlarged side view of a reticle assembly in accordance with another embodiment of the present invention, which embodiment includes showing two lens elements cemented together using an optically correct cement.

DETAILED DESCRIPTION

The invention provides a reticle in the first focal plane, which can be used both for close range and long range shooting. A phosphor luminescent material or other type of visible reflecting material is used with a diffraction grating to enhance the brightness or visibility of all or a portion of the reticle, and may be used alone or in connection with other ways of illuminating the reticle.

Throughout this application, the term “reticle pattern,” or simply “reticle,” refers to a group of one or more lines or other markings in the focal plane that may be used to assist the user with measurements or observation of positions of objects. By contrast, the term “reticle assembly” refers to the optical lens or assembly in which the reticle or reticle pattern is placed or constructed.

Unlike traditional reticle illumination, which typically involves the reflection of light from an LED off a reflective material, such as titanium dioxide, a diffraction grating works a bit differently. A diffraction grating causes light to be amplified by means of constructive interference when the light passes through the grating, and thereby provides an improved or amplified way to illuminate a reticle.

As shown in FIGS. 1-3, according to the present invention, the advanced illuminated reticle uses diffraction grating to amplify light using a diffraction pattern. A reticle lens 10 includes three elements, a rear (toward the observer) element 12, a front (toward the target) element 14 and a center element 16 positioned between the front element and the rear element. A reticle pattern 18 is formed on the forward plane of center element 16. In the same plane, there is a portion of the reticle pattern that is made using a diffraction grating 20 (i.e. a diffraction pattern). A light emitting source 22 is placed on the rearward plane 21 of the front element 14.

In the preferred embodiment the light emitting source 22 is a phosphorescent material which emits visible light upon excitation by a non-visible light source, such as an infrared (IR) or ultraviolet (UV) light. This light emitting source 22 used for illuminating the diffraction pattern 20 is aligned with the diffraction pattern so that greater illumination is presented to the user, that is, viewer perceives that area as an amplified portion of the reticle.

As shown in FIG. 2, a UV or IR LED 26 at the edge of the reticle transmits UV or IR (i.e., non-visible) light to the phosphorescent material in the light emitting source 22. The phosphorescent material creates visible light when it is excited from the UV or IR light source 26. Because the phosphorescent material of the light emitting source 22 converts the IR or UV light to visible light and because it is located behind and aligned with the diffraction pattern 20 (on the opposite side of the reticle from the observer's eye), it transmits light straight at the diffraction pattern, resulting in a very bright pattern. While the use of a phosphorescent material for reticle illumination is known in the art (see U.S. Pat. No. 7,502,166 to Stenton), the advanced reticle illumination of the present invention uses the phosphorescent material in conjunction with a diffraction grating for the purpose of very bright illumination.

In one embodiment, a second light source, a visible light LED 24, may be positioned so as to reflect directly off a portion of the reticle desired to be dimmer, such as the cross hairs shown in FIG. 4.

In addition to the configurations discussed above, the advanced reticle illumination design could also be used in a variety of configurations. For example, it could be used in conjunction with traditional titanium dioxide/sodium silicate for visible light reflection illumination and chrome for non-illuminated reticle features. This would put many different illumination intensities in one reticle at the same time. In another configuration there could be multiple portions of light emitting or transmitting sources which are brighter than the traditional illumination, but do not have a diffraction pattern in front of them and lie on the same plane as the rest of the reticle pattern so as to give three different levels of brightness in the same reticle and/or three different colors. For example, referring to FIG. 5:

-   -   Dimmest: sodium silicate/titanium dioxide light reflecting         surface (the largest figure, including the cross hair lines) 18     -   Medium brightness: phosphor illumination with no diffraction         pattern (the dots at the intersections of the cross hair lines)         28     -   Brightest: phosphor illumination aligned with a diffraction         pattern (the broken circle) 20

This could give the user the ability to have a very bright center pattern with “drop compensation” features at a medium intensity (since they are not being enhanced by a diffraction pattern but by themselves are brighter than traditional illumination) and the rest of the pattern could be traditionally illuminated for the rest of the subtensions or other features on the reticle. This would be another step in ultimate flexibility to the user.

Different phosphors and visible LEDs could be used to create different colors all in the same reticle. Materials having two different brightnesses, or colors, could be used to provide an easy way to determine two different sets of aiming points. The user could selectively turn on the dimmer portion of the reticle by itself, or the brighter portion by itself, for example, for long range, or close range shooting, respectively, using the same reticle.

Combined with a multifunction illumination control, in a sense an electronic or even mechanical switch, a user could select between multiple brightness intensities, colors, or illumination for different portions of the reticle. The reticle design described above may also be used with an electronic system which can allow the user to selectively switch between viewing different parts of the reticle: to use them all at the same time, individually, and selectively change the brightness between all of them. Examples of various combinations include, but are not limited to:

-   -   Illuminated center pattern with phosphor/diffraction grating         only.     -   Illuminated center pattern with phosphor/diffraction grating         combined with illuminated visible LED reflecting off of titanium         dioxide/sodium silicate filled pattern in two different         intensities and/or colors.     -   Illuminated visible LED reflecting off of titanium         dioxide/sodium silicate filled pattern only with the center         pattern turned off.

These combinations of illumination give the user the utmost in flexibility for any shooting situation. In the same riflescope, a user can zoom to lx magnification and turn on the daylight bright center pattern for close shooting situations, then zoom to high magnification and switch to or combine with traditional illumination of the rest of the reticle pattern for longer range shooting in low light situations.

While the function and construction of diffraction gratings are well known, an example of a diffraction grating 30 that could be used in the present invention is shown in FIG. 6. In that figure, the grating 30 is formed in a substrate 32 which is in effect element 16. The grating 30 is formed by etching or cutting a series of parallel grooves 34 in the substrate. The separation between the horizontal grooves 34 of the grating 30 is dependent on the wavelength, based upon well-known formulae. As can be seen there, the light waves 36 pass cleanly through the first surface of the substrate 32, continue through the substrate, and encounter the diffraction grating 30, whereupon the light waves pass through the transparent portions 38 between the grooves 34, while being stopped at the relatively more opaque areas of the grooves themselves, causing the constructive interference patterns shown.

FIG. 7 shows another embodiment, wherein the phosphorescent material 22 is implanted into a chrome liner 40 so as to ensure that as much as possible of the light from the phosphorescent material is transmitted in the desired direction, toward the diffraction grating 20. Also in this embodiment, only two hard lens elements 12 and 14 are provided, adhered together by a layer of optically correct cement 42. The thickness of the layer of cement 42 must be at least greater than the wavelength of the light emitted by the phosphorescent material 22. One commonly used phosphorescent material is in the red range, with a wavelength of about 630 nm. Often the layer of cement 42 is about 10-20 microns, so in this embodiment the cement alone provides sufficient separation to accommodate the formation of full waves before the diffraction grating is encountered. Too large a layer of cement, however, could bring about problems in alignment of the phosphorescent material with the diffraction grating. In this embodiment, the diffraction grating 20 is on the side of the element 12 facing forward toward the phosphorescent material 22, rather than away, as shown in the earlier figures, as the layer of cement 42 alone in this embodiment provides the separation required.

Another advantage to note about the phosphor/diffraction illuminated portions of the reticle when used by themselves is that because the LED at the edge of the reticle is UV or IR it is invisible to the human eye and will not create any undesirable halo effect from bouncing around the inside of the scope. With visible LED illumination, as used in the prior art, a user will often see a ring of light or “halo” around the edge of the field of view, which is distracting.

Although the invention has been herein described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims and the description of the invention herein. 

What is claimed is:
 1. A telescopic sighting device comprising: a focal plane; a reticle positioned in the focal plane, the reticle having a reticle pattern and a diffraction grating; a first light source; a light emitting substance excited by the first light source and illuminating the diffraction grating.
 2. A telescopic sighting device as recited in claim 1 further comprising a second light source illuminating at least a portion of the reticle pattern not in line with the diffraction grating.
 3. A telescopic sighting device as recited in claim 1 wherein the light emitting substance is a phosphorescent light source that emits visible light.
 4. A telescopic sighting device as recited in claim 3 wherein the phosphorescent light source is of the type that is excited by one of IR and UV light.
 5. A telescopic sighting device as recited in claim 4, wherein the first light source emits a non-visible light.
 6. A telescopic sighting device as recited in claim 2 wherein some of the light from the second light source illuminates some but not all of the reticle.
 7. A telescopic sighting device for use by a user, the sighting device comprising: a first sighting element having a focal plane; a reticle pattern formed in the first sighting element at the focal plane; a diffraction grating formed in the first sighting element at the focal plane; a first light source; a light emitting substance excited by the first light source and positioned in the focal plane, and aligned with the user and the diffraction grating so as to direct light through the diffraction grating to the user; a second light source for illuminating at least a portion of the reticle pattern.
 8. A telescopic sighting device as recited in claim 7 wherein the light emitting substance is a phosphorescent light source that emits visible light.
 9. A telescopic sighting device as recited in claim 8 wherein the phosphorescent light source is of the type that is excited by one of IR and UV light.
 10. A telescopic sighting device as recited in claim 9 wherein some of the light from the second light source illuminates some but not all of the reticle.
 11. A telescopic sighting device for use by a user, the sighting device comprising: a first sighting element having a focal plane; a reticle formed in the first sighting element at the focal plane; a diffraction pattern formed in the first sighting element; a light emitting substance positioned and aligned with the user and the diffraction pattern; and a first light source selected and positioned so as to excite the light emitting substance to direct the light through the diffraction pattern to the user.
 12. A telescopic sighting device as recited in claim 11 further comprising a second light source for illuminating at least a portion of the reticle pattern not in line with the diffraction pattern.
 13. A telescopic sighting device as recited in claim 11 wherein the light emitting substance is a phosphorescent light source that emits visible light.
 14. A telescopic sighting device as recited in claim 13 wherein the phosphorescent light source is of the type that is excited by one of IR and UV light.
 15. A telescopic sighting device as recited in claim 14 wherein some of the light from the first light source illuminates some but not all of the reticle. 